Flower production: Manage pitfalls before growing proteas


By Digital team | 18 October 2018
proteas
Photo: Gerhard Malan

Fynbos plants like proteas are area-specific and growing them can be challenging.

Protea species cannot be cultivated just anywhere. Most of them grow naturally on marginal soils in the Western Cape Province of South Africa and along the escarpment up to the Limpopo Province.

For commercial production, the climate should be cool and moist or hot and dry. Humidity increases the risk of leaf diseases and temperatures above 35ºC can reduce plant growth.

Hail nets can be used over plants to reduce hail damage, but make sure that plants still receive enough sunlight. Frost-prone areas are a no-no. Young shoots are sensitive to frost damage and flowers can be damaged to such an extent that they are no longer suitable for the market. Black frost can destroy plants.

SOIL PREPARATION

  • Dig soil profile holes 1.2 m deep to assess the depth and texture of the soil and the soil preparations needed before new plantations are established.
  • Soils should have a coarse sand content of more than 50% and a clay content below 20%.
  • The soil should be free-draining as soil-borne diseases can kill plants.
  • Fynbos plants require a soil depth of one metre or more for optimal growth.
  • Ridge the soil if it is too shallow and to maximise soil aeration after rains.
  • Soil samples should be taken at a depth of 0 cm to 30 cm and 30 cm to 60 cm from 5 to 8 sites per hectare.
  • Ideally, soils should be acidic with a pH at or below 5.5.
  • The phosphate content should be low, there should be a relatively low humus content and there should be more calcium than magnesium.
  • Old fields and orchards often contain weeds, which restrict the establishment and growth of new protea plantings.
  • Before preparing the soil, spray the weeds with a good systemic weed killer.
  • Spray concentrations should be in accordance with the instructions on the label.
  • Apply fertilisers before preparing the soil.
  • This is a chance to spread nutrients in the root zone.
  • All nutrient deficiencies in a soil depth of up to 70 cm can be remedied by pre-fertilisation to obtain optimal growth and full harvesting potential.
  • After soil preparation, mark out plant rows.
  • Limit traffic in the orchard to tractor rows to avoid soil compaction.

Also read: Do it yourself: Making your own basic soil pH test

COVER CROPS

  • Wind erosion can occur on sandy soils after soil preparation.
  • Sow oats between rows to prevent damage to young plants by “sand blasting”.
  • During the arid summers of winter rainfall areas, cut plant matter could be used as an organic mulch to keep moisture in the soil and control weed growth around the young plant or cutting.
  • Mulching is a general practice.
  • Black plastic, of 1 m wide and 30 microns thick, is currently the cheapest mulch.
  • Mulch helps to retain moisture and control weed growth while plants are young and sensitive to competition.
  • The temperature of the soil beneath the black plastic is higher than for soil that isn’t covered, which is advantageous for root development after a cold winter.
  • Organic mulches are preferred, as they will favour permeability of rain and aeration.
  • They can stimulate surface proteoid root development, both in the mulch and just below.
  • In summer rainfall areas, thin layers of organic mulch are used if it doesn’t cause a fire hazard in the winter.
  • Plastic mulches aren’t used in these areas as termites, moles and mice nest below the plastic, damaging the roots of plants.

PLANTING

Take the following into account when deciding on the plant density:

  • Type of cultivar or species.
    Dry land cultivation versus the use of irrigation.
    Quality of soil with regard to soil depth and type.
    The type and size of implements to be used between rows.

Traditional species and cultivars of Leucodendron and Leucospermum are cultivated in a standard format of 3 m by 1 m single rows, resulting in 3 333 plants/ha.

Double rows could also be used, but plants should be alternated and not planted opposite each other, since doing so could affect the application of pesticides. Double or multiple rows are only recommended for smaller, less complex or denser-growing plants.

If farms are small and land is limited, high-density plantings can be undertaken, if an effective spraying mechanism is available. If orchards are small enough to use rucksack sprayers or motorised rucksack sprayers, it will only be necessary to leave walking paths between plants.

In winter rainfall areas, where irrigation is not available, planting should occur as early as possible in winter (April, May, June) with the onset of the rainy season. Young plants will benefit from the winter rainfall, with better root development and establishment.

In the Eastern Cape Province, planting can be done from September to October. In irrigated orchards, plants can be established as late as October in the winter rainfall area.

In summer rainfall areas, dry land cultivation should be avoided. Planting should occur just after the first rains, as soon as the danger of severe cold and frost has passed.

Use small spades to make planting holes through the plastic mulch. The rooting bag should be torn carefully before being fully removed, to prevent too much disturbance to the root structure.

The plant is placed in the hole and soil is spread lightly around the plant before being lightly packed to stabilise the plant. Do not place material such as bone meal, pine needles or compost in the planting hole as this can disturb or affect full root development.

Plants should be watered as soon as possible after planting, either by watering car, watering can or drip irrigation system, to establish the soil around the roots and press out the air.

If orchards are planted against sloping contours or on slopes, the rows should run in the same direction as the contour to prevent erosion.

IRRIGATION

Use irrigation to achieve good quantities and quality. Overhead irrigation and micro sprinklers can damage flowers and promote the development of fungal diseases.

Drip irrigation has the following advantages:

  • Economic use of water.
  • Root systems develop in the irrigated areas.
  • Less stimulation of weeds growth.
  • Dissolved fertiliser can be applied through dripper lines.

Stem lengths can be increased by 250 mm and the vase life of flowers extended by a week through correct irrigation scheduling.

Good orchard establishment is obtained by irrigating young plants at a 20% depletion level of plant-available water.

FERTILISATION

  • Generally, soils in naturally occurring fynbos areas contain very low levels of potassium, magnesium, calcium and almost no phosphates.
  • Proteas evolved here and adapted to survive these conditions.
  • Call on an expert when planning the maintenance of your fertilisation programme. Maintenance fertiliser can be applied when plants are well-established and actively growing.
  • The nutritional requirement of proteas is very specific on ratios between elements in the soil such as calcium, magnesium and potassium.
  • Corrections should be made before preparing the soil and worked in deeply.
  • The annual harvesting of flower stems depletes nutrients and these must be replaced in the soil.
  • Nitrogen applications should be limited to ammonium sulphate.
  • Too-high ammonium levels hamper the growth of young plants.
  • In the past, it was alleged that phosphate levels of 12 parts per million and higher could cause toxicity.
  • It’s true that too-high levels of plant-available phosphate can hamper the growth and development of the whole plant.
  • Phosphates leach very little and bind quickly and strongly to soils after application.
  • Soils in South Africa, and more specifically the white sand in the natural fynbos areas, are relatively poor in potassium.
  • Leaf yellowing on the oldest leaves near the soil surface is often seen, especially on pincushions (Leucospermum).
  • Applying magnesium sulphate (Epsom salts) can improve stem length and leaf quality.

PRODUCTION PERMITS

All protea farmers and people using any type of material derived from indigenous plants in South Africa, require a permit available from the offices of the Department of Nature and Environmental Affairs. Enquiries should be made about which permits are required.

Consult exporters, marketers, scientists and fynbos experts about what to plant, and order cultivars well in advance.
Rooted cuttings, well-hardened off, are used for planting.

It takes 3 to 5 years before protea plants start to flower annually.

  • This article was written by Dr. Emmy Reinten and first appeared in Farming SA.